The functions of a calcium-binding protein isolated from brain in this laboratory will be investigated in this phase of the project. We have recently demonstrated that this protein CBP II (or CDR) is found at very high levels in electric tissue of electric eel. Whereas in brain, this protein activates enzymes which synthesize and breakdown cyclic nuceotides in electroplax the protein does not activate either enzyme. We will further examine the regulation of neuronal activity in electric tissue as this preparation will permit the study of synaptic activity in a system consisting of only one type of synapes. In other phases of this study we will study the regulation of CBP II levels in nervous tissue and the phosphorylation if this protein. BIBLIOGRAPHIC REFERENCE: Calcium-binding Proteins in Electroplax and Skeleta Muscle. Comparison of the Parvalbumin and Phosphodiesterase Activator Protein of Electrophorus electricus, S.R. Childers and F.L. Siegel (1976) Biochim. Biophys. Acta 438, 316-325. Regional, Cellular and Subcellular Distribution of Calcium-activated Cyclic Nucleotide Phosphodiesterase and Calcium-Dependent Regulator in Porcine Brain. J.C. Egrie, J.A. Campbell, A.L. Flangas, and F.L. Siegel, J. Neurochem. In Press.